LIFE SCIENCE

Detailed explanation-1: -The difference in the side-chain group or R-group is what determines the unique properties of each amino acid.

Detailed explanation-2: -The carbon, carboxyl, and amino groups are common to all amino acids, so the R-group is the only unique feature in each amino acid.

Detailed explanation-3: -The twenty amino acids (that make up proteins)each have assigned to them both three-letter (can be upper or lower case) and one-letter codes (upper case). This makes it quicker and easier for notation purposes and are worth learning.

Detailed explanation-4: -The essential amino acids are histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine. The nonessential amino acids are alanine, asparagine, aspartic acid, glutamic acid, and serine.

Detailed explanation-5: -Which of the following parts of an amino acid vary among different amino acids? While all amino acids contain an amino group, a carboxyl group and a hydrogen bound to the central carbon, the R groups vary among the 20 different amino acids.